Low profile protective enclosure for wellhead apparatus

ABSTRACT

Low profile wellhead installation and servicing apparatus for subsea wellhead assemblies and the like, including a conductor guide conduit having a protective enclosure fixed to the upper extremity thereof. The guide conduit and protective enclosure are inserted into surface stratum to such extent that the upper extremity of the enclosure is located substantially at the surface level of the surface stratum, thereby presenting an extremely low profile that is not susceptible to damage by equipment ordinarily employed above the surface stratum or by other foreign objects. The guide conduit and enclosure structures are provided with means to wash the conduit and enclosure to their proper depth in the surface stratum during installation and also include a system for filling same with corrosion and marine life inhibitors or removing the inhibitors as desired. The apparatus includes a service manipulator which is receivable within the enclosure and is capable of performing various repair operations.

United States Patent [72} lnventor Norman A. Nelson Houston, Tex.

[21] Appl. No. 836,362

[22] Filed June 25, 1969 [45] Patented July 13, 1971 [73] Assignee A C F Industries Incorporated New York, N.Y.

[54] LOW PROFILE PROTECTIVE ENCLOSURE FOR WELLHEAD APPARATUS 13 Claims, 12 Drawing Figs.

[521 US. Cl. 166/5, 166/244 0 s11 lnt.Cl E 2l b 33/035 501 Field of Search 166/5, .6,

Primary Examiner.lames A. Leppink Artorney-James L. Jackson ABSTRACT: Low profile wellhead installation and servicing apparatus for subsea wellhead assemblies and the like, including a conductor guide conduit having a protective enclosure fixed to the upper extremity thereof. The guide conduit and protective enclosure are inserted into surface stratum to such extent that the upper extremity of the enclosure is located substantially at the surface level of the surface stratum, thereby presenting an extremely low profile that is not susceptible to damage by equipment ordinarily employed above the surface stratum or by other foreign objects. The guide conduit and enclosure structures are provided with means to wash the conduit and enclosure to their proper depth in the surface stratum during installation and also include a system for filling same with corrosion and marine life inhibitors or removing the inhibitors as desired. The apparatus includes a service manipulator which is receivable within the enclosure and is capable of performing various repair operations.

PATENTED JUL 1 a l97| SHEET 1 BF 6 Normcn A. Nelson INVE N TOR A TTORNE Y ATENTED JUL 31971 SHEET 2 [1F 6 Norman A. Nelson INVENTOR ATTORNEY PATENIED JUL13|97| 7 3592.263

SHEET 3 [IF 6 Norman ANe/son INVENTOR BZMW A TTORNEY PATENIED JUL] 3 Ian SHEET 0F 6 FIG. 6

W VE N TOR A TTORNEY.

PATENTEU JUL I BE?! SHEET 5 0F 6 Norman A. Nelson IN VE N TOR FIG. 70

A 7 TORNE Y PATENTEI] JUL 1 3 l97| SHEET 6 OF 6 Norman A.Nelson IN VE NTOR FIG. 77

A TTORNEV LOW PROFILE PROTECTIVE ENCLOSURE FOR WELLHEAD APPARATUS BACKGROUND OF THE INVENTION The present invention relates generally to wellhead apparatus and more particularly to wellhead apparatus which is installed at or adjacent to the ocean floor.

Offshore wellhead installations may be accomplished in a number of different ways, such as by installing platforms extending above the surface of the ocean or by installing the wellheads above the ocean floor but a considerable distance from the ocean surface so as to prevent interference by surface vessels or the like. Wellhead apparatus are also installed with the wellhead resting upon the ocean floor. When wells are completed with the wellhead apparatus positioned above the ocean floor, the apparatus is susceptible to damage by anchor cables or by other objects moving through the water in the vicinity of the wellhead.

In order to provide for long life of subsea wellhead assemblies, it is considered desirable to minimize the undesirable effects of corrosion and to prevent marine life from interfering with servicing operations.

It is also deemed advisable to provide subsea wellhead installations with remotely or manually controlled repair'equipment in order to provide for repair and/or replacement of valve parts and other wellhead equipment.

Accordingly, it is a primary object of this invention to pro- 'vide a novel wellhead installation allowing the wellhead to be positioned adjacent to or below the surface level of the ocean floor in order to prevent damage to the wellhead assembly by foreign objects.

Another object of this invention is to provide a novel wellhead installation allowing wellhead to be completely enclosed to prevent damage to the wellhead by external objects and to prevent the enclosure from filling with sand or silt.

It is an even further object of this invention to provide a novel wellhead installation including an enclosure surrounding the wellhead which may be filled with corrosion and marine life inhibitors to protect the wellhead apparatus and which includes apparatus allowing removal of the inhibitors in the event servicing of the wellhead is desired and permits filling of the enclosure with a clean filtered water to provide good visibility for monitoring the servicing operation.

Another object of this invention contemplates the provision of a novel wellhead installation and repair system including a manipulator mechanism that may be lowered into the enclosure and which is capable of performing various repair operations as desired.

Among the several objects of this invention is contemplated the provision of a low profile protective installation for wellheads that is provided with means to accomplish insertion of the protective apparatus into the surface stratum at the well location.

It is still another object of this invention, to provide a low profile protective wellhead installation which is simple in nature, reliable in use and low in cost.

Other and further objects, advantages and features of this invention will become apparent to one skilled in the art upon consideration of the written specification, the attached claims and the annexed drawings. The formof the invention, which will now be described in detail illustrates the general principles of the invention, but it is to be understood that this detailed description is not to be taken as limiting since the scope of the invention is thus defined by the appended claims. Such description will be referred to by reference characters in the drawings in which:

FIG. 1 is a sectional view of the low profile subsea wellhead enclosure structure of this invention having a wellhead mechanism located therein and shown in elevation.

FIG. 2 is a sectional view of the protective enclosure of FIG. I having the cover removed and illustrating washing the enclosure into place.

FIG. 3 is a sectional view of the protective enclosure structure of FIG. I illustrating the enclosure in place within the surface stratum of the ocean floor and showing landing of the surface casing.

FIG. 4 is a partial sectional view in elevation illustrating the protective enclosure of this invention and showing installation ofa wellhead assembly and Christmas tree assembly therein.

FIG. 5 is an elevational view illustrating the profile ofa fully installed and sealed subsea wellhead protective enclosure installation according to the teachings of this invention.

FIG. 6 is a fragmentary sectional view of the cover structure of the protective enclosure illustrating the fluid transfer con nection structure.

FIG. 7 is a fragmentary sectional view of the cover structure of the protective enclosure illustrating the stabbing pin arrangement utilized for filling the enclosure with preservative fluid.

FIG. 8 is a fragmentary sectional view ofthe cover structure of the protective enclosure illustrating the stabbing pin arrangement utilized during removal of preservative fluid from the enclosure.

FIG. 9 as a fragmentary sectional view of the cover structure of the protective enclosure illustrating a pressure balancing closure member fixed to and closing the fluid transfer connection structure of this invention.

FIG. 10 is an elevational view illustrating the repair manipulator of this invention and showing the work platform in two positions.

FIG. 11 is a sectional view of the protective enclosure structure of this invention with the manipulator installed in operating position within the enclosure.

FIG. 12 is a plan view illustrating the repair manipulator structure of FIG. 10.

Briefly the invention concerns a protective wellhead installation facilitating installation of a wellhead and Christmas tree assembly below the surface level of the ocean floor to afford protection against damage by foreign objects. The invention is accomplished by providing a protective enclosure within which the subsea wellhead assembly is located, which enclosure is of sufficient dimension to allow the introduction of a subsea repair manipulator for the purpose of performing various repair operations to the wellhead valves and other parts of the wellhead assembly. The protective enclosure is specifically designed to guide or properly orient the repair manipulator in order that repair operations may be accurately performed. The protective enclosure is provided with external means which allow the protective enclosure and a conductor guide conduit to which the enclosure is attached to be washed into the surface stratum of the ocean floor simply by pumping fluid under pressure through the conductor guide conduit causing the surface stratum to be washed away about the conductor guide conduit and protective enclosure. The protective enclosure is also provided with a plurality of drag blades on lower surfaces thereof which in addition to providing a strengthening function for the protective closure also provides structure for agitating the surface stratum as the protective enclosure is rotated by drilling apparatus. As the surface stratum is agitated by the drag blades, circulating fluid pumped through the conductor guide conduit will wash away the surface stratum allowing the protective enclosure and conductor guide conduit to settle until landing flanges provided on the protective enclosure contact the surface level of the ocean floor.

After installation of the protective enclosure structure to its proper level in the surface stratum, normal drilling and completion operations may be carried on within the protective enclosure. After the well has been completed and the wellhead assembly including Christmas tree assembly has been properly set in place, a protective cover is lowered into assembly with the protective enclosure, thereby completely enclosing the wellhead assembly. The sealed enclosure is then filled with corrosion and marine life inhibitors in order to protect the wellhead assembly in its submerged state. The protective enclosure.

A repair manipulator mechanism is receivable within the protective enclosure and is capable of installing the removing 'valve operators and valve part assemblies in addition to performing various other repair operations.

With reference now to the drawings for a better understanding of this invention, in FIG. 1 is shown a generally cylindrical protective enclosure 10 having a generally cylindrical sidewall 12, an 7 upper frustoconical bottom wall 13 and a. lower frustoconical bottom wall 14, interconnected by a small cylindrical wall 15. The bottom wall vl4 is connected by welding or the like to a conductor guide casing 16 of tubular construction which may extend a considerable depth below the protective enclosure 10. For example, the conductor guide assembly may be in the order of 200 .feet in length. The bottom of the conductor guide casing is rounded as illustrated in FIG. and is provided with one or more openings through which pressurized fluid such as water may flow as the conductor'guide casing and theprotective enclosure are washed into placeas described in detail hereinbelow. A number of ribs or drag blades 20 and 21 are fixed to the exteriorof the bottom walls 13 and 14 respectively, to serve both to strengthen the bottom walls during service conditions of the protective enclosure and to agitate the surface stratum as the protective enclosure and conductorv guide mechanism are washed to their proper position. A plurality of centering elements 22 are provided either interiorly of the conductor guide casing 16 or exteriorly of a centering sleeve structure 24, receivable within the conductor guide casing. The purpose of the centering sleeve is to properly orient drill pipe or stem 26 and other conduit structure which might extend through the conductor guide casing. Obviously, a separate centering sleeve is required for any particular size of drill stem or casing extending through the con ductor guide casing.

For the purpose of washing the protective enclosure. and conductor guide casing to the proper depth with respect tothe surface stratum, the drill pipe 26 extends through the centering sleeve 24 and is disposed in fluid communication'with the jetopenings I8 at the bottom of the conductor guide casing in such manner as to force pressurized fluid outwardly through the jet openings 18. The drill pipe 26 is connected to suitable fluid pressurizing apparatus such as pumpstructure located on a drilling vessel or platform capable of forcing high-pressure fluid, such as water, outwardly through the jet openings 18, in order to wash away the surface stratum and allow the conductor guide casing to settle into the void-defined by therdisplaced stratum. After the conductor guide casing 16 is completelyinserted into the surface stratum, the substantially larger. protective enclosure will begin to enter into the surface stratum as washing is continued. Pressurized fluid pumped through the jet openings 18 will continue to circulate about the conductor guide casing and protective enclosure and willwash away the surface stratum under the protective enclosure allowing the enclosure also to settle within the surface stratum. In theevent agitation of the surface stratum is necessary to achieve the.

' face of the ocean floor. The conductor guide casing 16 and the attached protective enclosure 10 are then cemented-into place by circulating cement through the drill stem 26 and outwardly around the protective enclosure. In the event the surface stratum is of sufficient hardness that washing the enclosure its proper depth is impractical, it is obvious that a hole may be vessel or platform performing the drilling operation. A guide frame 34 is adapted to travel on the cables 32 upwardly and downwardly relative to the protective enclosure and serves to guide various tools and equipment into proper assembly with the protective enclosure. The guide frame34' includes guide receptacles 36 received by the guideposts 30 as the guide frame is lowered into proper assemblywith the protective e nclosure. The guide receptacles 36 are provided with apertures 38 receiving the cables 32 in guiding relation therewith".

After the protective enclosure 10 and the conductor guide casing are properly cemented into place, as illustrated in FIG; 3, a temporary extension sleeve 40 is attached to the upperextremity of the cylindrical wall 12 to serve as a barrier during drilling operations to prevent sand or other foreil r matter from the ocean floor from entering the interior of the protective enclosure. The upper portion of the well is then drilled and surface casing 42 is landed on the upper portion of the centering guide 22 and is cemented into place. At theupper portion of the surface casing 42 is located a casinghanger shoulder 44 provided for landing and orienting other casing and tubing in telescoping relation with the surface casing. Obviously, any other acceptable casing, tubing and wellhead arrangement may be employed within the spirit and scope of this invention.

As shown in FIG. 4, the well is completed by the installation of a wellhead assembly illustrated generally at 46 including a wellhead mechanism 48, a Christmas tree assembly 50and a valve control system 52 for selectively operating the valves of the Christmas tree assembly 50. The temporary extension sleeve 40 is removed prior to installation of the wellhead assembly within the protective enclosure 10. The Christmas tree '50 includes a plurality of valves 54, each'be ing actuated by a remotely controllable power operator to control the flow of fluid through the Christmas tree production conduit structure. Hydraulic power may be provided for controlling the various hydraulic valve operator by the self-contained hydraulic power pack or valve control system 52, or various other conventional valveactuation means may be incorporated into the wellhead assembly within the spirit or scope of the instant invention.

The wellhead assembly is providedwith at least one production conduit 58 extending from the Christmas tree 50 to'an'ap- 'propriate storage or fluid handling facility for petroleum products being produced by the well. A generally cylindrical permanent extension 60 is connected in sealed engagement to the upper extremity of the cylindrical wall 12 and provides for sealed extension of the'production conduit through: the protective enclosure 10. The extension 60 is permanently welded or otherwise fixed to the productionconduit before installation of the wellhead assembly and is'lowered into assembly with the cylindrical wall 12 along with the Christmas tree assembly. This feature prevents any necessity for providing an opening in the enclosure wall which must be sealed about the production flow conduit after the conduit is installed.

Connection between sections of the production conduit 58 may be'established by means of remotely actuated flow line connectors, such as illustrated at 62 in FIG. 4. Various connections between the Christmas tree structure '50 andother structure of the wellhead assembly 46 may be accomplished by any one of a number of acceptable remotely actuated-connector devices, thereby allowing the Christmas tree assembly After the well has been completed and the wellhead assembly has been installed, a protective cover structure 64 is lowered by the guide frame 34 into sealed assembly with the upper portion of the extension sleeve 60. A fluid transfer connection 66 is fixed to the protective cover 64 and comprises a stabbing sleeve 67 welded or otherwise fixed to the cover structure 64. The fluid transfer connection structure is employed to fill the protective enclosure with a preservative substance including corrosion inhibitors and agents to prevent the growth of marine life. The same fluid transfer connection structure is employed to remove the preservative substance from the protective enclosure simply by changing internal fluid passage structure of the fluid transfer structure by means of threaded plugs as will be described in detail hereinbelow. The stabbing sleeve is provided with a through passage 68 having a pair of internal cylindrical surfaces 69 and 70 providing sealing surfaces for engagement by a pair of spaced sealing members 71 and 72, respectively, carried by a stabbing pin 73 receivable within the sleeve 66. The sleeve 66 is also provided with internal threads 74 at the upper extremity thereof for receiving a closure plug 75 as illustrated in FIG. 9. If desired, the stabbing pin may also be provided with external threads received by the internal threads 74 in order to establish a secure connection between the stem 26 and the cover structure 64. The stabbing pin 73 is provided with an upper internally threaded blind depression 76 to which the drill stem 26 is threadedly connected as shown in FIGS. 7 and 8. A pair of generally parallel fluid transfer passages 77 and 78 are formed in the stabbing pin 73 and are disposed in fluid communication with the depression 76. Passage 77 extends substantially straight through the stabbing pin terminating at the bottom of the pin in order to conduct fluid directly between the protective enclosure and the drill stem 26. The passage 77 is threaded at its upper extremity in order to receive a threaded plug 79 as shown in FIG. 7. A transverse passage 80 communicates passage 77 with the atmosphere or with the medium surrounding the stabbing stem and is internally threaded at its outer extremity for the purpose of receiving a closure plug. The passage 78 is communicated to the medium surrounding the stabbing pin or to a return conduit 81 through a transverse passage 82 also being threaded at its outer extremity in order to receive a closure plug such as is shown in FIG. 7 or to receive a return conduit as illustrated in FIG. 8. Passage 78 is also communicated by another transverse passage 83 with an annular chamber 84 defined about the pin 73 due to the different diameter of the surfaces 69 and 70. A displacement conduit 85 is welded or otherwise fixed to the stabbing sleeve 67 and establishes fluid communication with the annular chamber 84. A conduit 85 is connected with a second displacement conduit 86 fixed outwardly of the protective enclosure by a remotely controlled connection mechanism 87.

If desired, the stabbing sleeve can be fixed at a lower point to the cover 34 or may be manufactured slightly longer as illustrated in broken lines in FIGS. 1 and 6 in order to allow the displacement conduit shown in broken lines at 88 to be located within the protective enclosure 10 when the protective enclosure is closed by the cover structure 34. In such case, the displacement conduit is installed and removed simultaneously with installation and removal of the cover 34 and an automatic connection structure is not required.

With reference now to FIG. 7, for the purpose of filling the protective enclosure 10 with a fluid substance containing corrosion and marine life inhibitors and being heavier than water, the stabbing pin 73 is arranged with a closure plug 79 closing the upper extremity of the passage 77 and with a second closure plug closing the transverse outlet passage 82. The preservative fluid may be pumped from the platform through the drill stem 26 to the stabbing pin structure 73 where it will flow through passage 78 and transverse passage 83 to the displacement conduit structure 85 and 86. The preservative fluid will exit from the displacement conduits through the opening 87 at the lowermost portion of the protective enclosure and, being heavier than sea water, will displace the sea water upperwardly causing sea water within the protective enclosure to exist through the passage 77 and the transverse outlet passage 80. If desired, a return conduit may be connected to the threaded portion of the transverse outlet passage allowing the displaced sea water and preservative fluid to be transported to the platform for handling. Ordinarily, it is more appropriate to vent the sea water from the enclosure into the sea.

After sufficient preservative fluid has been pumped into the protective enclosure to completely fill the same, a pressure balancing closure 89 may be threadedly received within the upper extremity of the stabbing sleeve 67 essentially as illustrated in FIG. 9. An annular sealing member 90 is carried at the lower extremity of the closure 89 and engages the sealing surface 69 of the stabbing pin 67 in order to establish a fluid passage seal between the closure and the stabbing pin.

In the event servicing of the subsea wellhead is required it will be necessary to remove the preservative fluid from the enclosure. This is accomplished by closing the upper extremity of the passage 78 with a plug and by closing the transverse outlet passage 80 with a plug as shown in FIG. 8. The outlet passage 82 may either be open to the medium surrounding the connection structure or a return conduit 81 may be connected as shown in FIG. 8 in order to conduct displaced preservative fluid to the drilling platform or vessel. To displace the preservative fluid from the enclosure 10, water is pumped through the drill stem 26 and through the passage 77 into the upper extremity of the closure as shown by small flow arrows. This causes the preservative fluid within the enclosure 10 to be forced upwardly through the displacement conduits 86 and and into the passage 78 of the stabbing pin 73. The preservative fluid may then be either displaced directly into the sea through the transverse outlet passage 82 or the fluid may be transported to the drilling platform through the return line 81 for storage and reuse.

Removal of the preservative fluid from the enclosure 10 may also be accomplished by removing the cover 34 and by simply pumping the preservative fluid out of the uncovered enclosure.

In the event the preservative substance is lighter than sea water, the filling and removing operations obviously will be substantially reversed.

For the purpose of balancing fluid pressure within the protective enclosure 10 at all times, the pressure balancing closure 89 is provided with a pair of fluid passages 91 and 92 each being provided with spring-biased check valves 93 and 94, respectively. In the event fluid pressure within the protective enclosure should increase above the hydrostatic pressure of the seater surrounding the enclosure, the outlet check valve 94 will be displaced from its seat and fluid pressure will be allowed to bleed into the sea water. A reduction of fluid pressure within the protective enclosure 10 below the hydrostatic head of the sea water will cause the inlet check valve 93 to be displaced from its seat allowing sea water to enter and balance the internal pressure with pressure externally of the protective enclosure. This feature allows the protective enclosure structure to be fabricated of relatively light material, since it is not subjected to extremely great differential pressures.

After the drill pipe 26 has been disconnected from the fluid transfer connection structure 66 and the pressure balancing closure 89 has been installed, the extension 60'and protective cover 64 for the enclosure 10 will extend above the surface of the ocean floor essentially as illustrated in FIG. 5. The production flow conduit 58 will exit from the protective enclosure near the level of the ocean floor, thereby precluding any tendency of the production flow conduit to be damaged by foreign objects. The low silhouette of the protective enclosure and the relation of the wellhead and Christmas tree to the ocean floor will preclude any probability of injury to the subsea wellhead mechanism by objects moving through the ocean at the level of the ocean floor.

With reference now to FIGS. 9 and 10, for the purpose of repairing the valves of the Christmas tree assembly and for performing other'repair operations, a repair manipulator, il-

lustrated generally at 95, is lowered into the protective enclosure 10 after the cover structure has been removed The repair manipulator includes a vertical support column 96 receiving a work platform 97 in sliding engagement therewith. The work platform 97 is moved to any position along the .length of the column 96 by a control cable 98. An electrically or hydraulically energized motor 99 is remotely controllable in order to raise or lower the work platform 97 to any suitable operating position thereof. The work platform 97 includes an extendable work shelf 100 carrying a valve operator manipulating device 102 or other suitable work apparatus. The work platform 97 also includes a power-operated wrench 104 carried by the work shelf 100 which may be driven by hydraulic or electrical energization as desired, and includes a drive socket 106 capable of engaging the drive nut 108 of a valve operator in the manner illustrated in H6. 10. The upper extremity of the manipulator is provided with support wheel structure 110 capable of engaging the uppermost portion of the extension 60 or enclosure rim essentially as shown in FIG. 10. The support wheel structure 110 is driven by the motor structure 99 in order to move the manipulator mechanism about the interior of the protective enclosure 10. The manipulator is oriented within the protective enclosure 10 by a pair of guide wheels 112 engaging the wall 12 of the enclosure. As shown particularly in FIGS. 10 and 11, the work platform 97 is pivoted at 114 about the vertical support member 92. A pair of lateral hydraulic cylinders 116 and 118 are remotely controllable from the drilling platform and serve to positively orient the work platform relative to the valve operator mechanism to be serviced. A second work shelf 120, essentially a duplicate of the work shelf 100, is provided for the purpose of supporting a second valve operator mechanism to be installed into thewellhead valve that is in need of service. The work platform 97 may include a television camera or other suitable apparatus for monitoring the work being done and the television camera may have the capability of panning or pivoting universally so that any work being done on any part of the enclosure may be monitored. Also, the work shelf itself may be capable of universal movement.

In operation, the manipulator 95 is lowered into the protective enclosure until the drive wheel mechanism 110 engages the annular rim of the protective enclosure. The work platform 97 is then lowered or raised by the motor 99 to the desired level of the valve operator to be serviced and the hydraulic cylinders 116 and 118 are remotely controlled in order to positively align the appropriate work shelf 100 or 120 with the appropriate valve operator. The motor 99 may also be controlled to move the manipulator about the interior of the enclosure for lateral alignment. The work shelf 100 or 120 is then energized causing the clamp members 102 to move into supporting engagement with the valve operator 56. The drive motor 104 and its drive socket 106 are then moved outwardly to engagement with the nut 108 of the valve operator 56 and the nut 108 is rotated by the socket 106 causing the valve operator to release its connection with the wellhead valve body. The work shelf 100 is then moved outwardly in order to extract the valve operator 56 along with the internal parts of the valve and the work platform 97 is indexed over in such manner as to align the second work shelf 120 with the valve body upon which repair is being performed. The hydraulic cylinders 116 and 118 may again be remotely manipulated in order to positively align the valve operator structure carried by the second work platform 120 with the valve being repaired. Ordinarily, misalignment will not occur by indexing,

but ifit does any minor misalignment may be corrected by the hydraulic alignment cylinders 116 and 118. The second work shelf 102 is then extended in such manner as to insert the internal valve parts within the valve and to move the valve operator structure into position allowing the collet clamps thereof to engage appropriate flange structure formed on the valve body. For such structure as is necessary for an understanding of the particular valve operator mechanism illustrated in this application, reference may be had to U.S. Pat.

application, Ser. No. 697,706, of Norman A. Nelson filed Jan. 15, 1968. it is to be understood, however, that other valve operator mechanisms of similar nature might be employed without departing from the spirit or scope of this invention. Also, it is anticipated that the repair manipulator might be provided with other repair structure than the particular mechanism shown for removal and replacement of valve operator mechanisms or other parts.

In view of the foregoing, it is clearly apparent that I have provided a novel subsea wellhead protective mechanism allowing the wellhead to be positioned below the surface of the ocean floor in order to protect the wellhead structure from damage by foreign objects moving through the area of the wellhead location. The protective enclosure of my invention also prevents sand, mud or silt from being deposited about the subsea wellhead structure and also provides for protection of the wellhead structure against corrosion and damage by marine life. The wellhead installation of my invention effectively provides production flow conduit structure which exits from the protective enclosure of this invention substantially horizontal with respect to the ocean floor and at the level of the ocean floor even though smooth radius production conduit structure is supplied to allow well tools to be pumped into the well in conventional manner. The protective enclosure of my invention also provides a stable environment surrounding the wellhead to prevent erosion of the surface stratum in the event the wellhead or Christmas tree structure should develop a leak, thereby promoting the ease of repairing the wellhead structure. Repair of the Christmas tree valve and valve operator assemblies is accomplished by a unique repair manipulator mechanism that is remotely controllable from a drilling vessel or platform to remove and replace various parts without necessitating diver assistance. Also, the manipulator is capable of being controlled manually by a diver to accomplish the various repair operations.

Having thus described the invention, what 1 claim to be new and what is desired to be secured by letters patent is:

1. A protective enclosure system for subsea wellhead apparatus comprising a conductor guide conduit extending a considerable depth into the surface stratum of the ocean floor, a protective wellhead enclosure being fixed at its lower extremity tothe upper extremity of said conductor guide conduit, the upper extremity of said enclosure being located near the surface level of the ocean floor, said enclosure receiving a wellhead therein in such manner that the wellhead is located below the level of the ocean floor, a removable closure member sealing the upper extremity of said enclosure in the closed condition thereof, said enclosure being normally filled with corrosion and marine life inhibitors, said guide conductor and enclosure receiving a drill pipe connectable to fluid pumping apparatus for washing away the surface stratum of the ocean floor thereby allowing said guide conductor and enclosure to settle, said enclosure having a plurality of drag blades fixed to the lower surfaces thereof for mechanically agitating the surface stratum of the ocean floor under said enclosure whereby fluid pumped through said guide conductor and around said enclosure will wash away the mechanically agitated surface stratum under said enclosure allowing said enclosure to settle to its proper depth relative to the ocean floor.

2. A protective enclosure as claimed in claim 1, a landing flange being fixed to said enclosure and resting on the ocean floor when said enclosure is inserted to its proper depth within the surface stratum of the ocean floor.

3. A protective enclosure as recited in claim 1, the production and control conduit means of the wellhead extending in sealed relation through said closure means, whereby said closure may be lowered into sealed assembly with said enclosure as the wellhead is lowered into said enclosure.

4. A protective enclosure as recited in claim 1, an extension sleeve secured to the production conduit .of said wellhead and moving into sealed assembly with the upper extremity of said enclosure as the wellhead assembly is lowered into said enclosure.

5. A protective enclosure as set forth in claim 1, a fluid transfer connection being fixed to said closure and having an opening into said enclosure, means being received by said fluid transfer connection for remotely filling said enclosure with said corrosion and marine life inhibitors, a displacement conduit being fixed to said fluid transfer connection and terminating at the lower portion of said enclosure for remotely removing said corrosion and marine life inhibitors from said enclosure for servicing.

6. A protective enclosure as recited in claim 1, guide means fixed to said enclosure and being connectable to a surface vessel, said guide means orienting said wellhead and said closure upon assembly thereof to said enclosure, said guide means also serving to guiding remotely controllable repair apparatus.

7. Low profile wellhead installation and servicing apparatus comprising a conductor guide conduit extending a considerable depth into the surface stratum of the earth, aprotective enclosure connected at the lower extremity thereof to said conductor guide conduit, the upper extremity of said enclosure being located adjacent the surface level of the surface stratum, a well casing extending through. said conductor guide conduit and terminating in a casing hanger at the lower extremity of said enclosure, a wellhead assembly connected to said casing hanger and having its upper extremity disposed substantially at the surface level of the surface stratum, at least one production conduit extending from said wellhead assembly, a removable extension normally being disposed in sealed assembly with the upper extremity oi said enclosure, said production conduit extending in sealed relation through said extension in generally horizontal manner substantially at the surface level of the surface stratum, a removable closure normally disposed in sealed assembly with the upper extremity of said extension.

8. Low profile wellhead installation and servicing apparatus as recited in claim 7, guide means fixed to said enclosure and extending to a location remote from said wellhead installation, said wellhead assembly being oriented by said guide means upon installation thereof within said enclosure.

9. Low profile wellhead installation and servicing apparatus as recited in claim 7, said extension defining a support rim, a service manipulator adapted to be guidingly supportable by said rim and being receivable within said enclosure, said servicing manipulator being oriented within said enclosure by the inner surface of said enclosure, s'aid manipulator being cap'able of accomplishing various repair operations:on said wellhead.

10. A protective enclosure for subsea wellhead apparatus comprising a conductor guide conduit extending a considerable depth into the soft surface stratum of the ocean floor, a wellhead protective enclosure connected to the upper extremity of said conductor guide conduit, the upper extremity of said enclosure being located substantially at the level of the ocean floor, the inner surface of said enclosure defining annular guide surface means, said enclosure defining an annular manipulator support rim at the upper extremity thereof, external guide means secured to said enclosure and being attachable to surface vessel structure, repair manipulator means being guidable into assembly with said enclosure by said external guide means, said repair manipulator being supported by said manipulator support rim and being oriented within said enclosure by said annular guide surface means, said manipulator being capable of moving about within said enclosure and performing various repair operations.

' 11. A protective enclosure system for a subsea wellhead assembly including a guide conductor extending a considerable distance into the surface stratum of the ocean floor, a protective enclosure fixed to the upper extremity of the guide conductor and having the upper extremity thereof disposed adjacent the surface level of the ocean floor, a cover member closing the upper extremity of the enclosure and preventing entry of foreign matter into said enclosure, fluid transfer apparatus secured to said cover and including a stabbing sleeve having a central opening, a fluid transfer conduit extending from said stabbing sleeve in fluid communication with said central openlng and terminating within said enclosure, a dllll stern having a stabbing pin disposed at the lower extremity thereof, said stabbing pin being receivable within said stabbing sleeve, said stabbing pin having fluid passages therein to selectively allow the filling of said enclosure with a preservative substance and to displace said preservative material from said enclosure.

12. A protective enclosure as set forth in claim 11, said stabbing pin having a pairof fluid transferpassages, one of said circuits being plugged to allow the filling of said enclosure with preservative and causing fluid to flow in one direction within said displacement conduit, the other of said fluid transfer passages being plugged to cause the flow of fluid through said displacement conduit in the opposite direction to cause displacement of preservative substance from said enclosure.

13. A protective enclosure as set forth in claim 11, a closure being receivable within said stabbing sleeve to seal said enclosure, said closure having pressure balancing valve means therein to maintain a substantially balanced condition,

between said protective enclosure and the hydrostatic head of the sea water at the depth of the enclosure. 

1. A protective enclosure system for subsea wellhead apparatus comprising a conductor guide conduit extending a considerable depth into the surface stratum of the ocean floor, a protective wellhead enclosure being fixed at its lower extremity to the upper extremity of said conductor guide conduit, the upper extremity of said enclosure being located near the surface level of the ocean floor, said enclosure receiving a wellhead therein in such manner that the wellhead is located below the level of the ocean floor, a removable closure member sealing the upper extremity of said enclosure in the closed condition thereof, said enclosure being normally filled with corrosion and marine life inhibitors, said guide conductor and enclosure receiving a drill pipe connectable to fluid pumping apparatus for washing away the surface stratum of the ocean floor thereby allowing said guide conductor and enclosure to settle, said enclosure having a plurality of drag blades fixed to the lower surfaces thereof for mechanically agitating the surface stratum of the ocean floor under said enclosure whereby fluid pumped through said guide conductor and around said enclosure will wash away the mechanically agitated surface stratum under said enclosure allowing said enclosure to settle to its proper depth relative to the ocean floor.
 2. A protective enclosure as claimed in claim 1, a landing flange being fixed to said enclosure and resting on the ocean floor when said enclosure is inserted to its proper depth within the surface stratum of the ocean floor.
 3. A protective enclosure as recited in claim 1, the production and control conduit means of the wellhead extending in sealed relation through said closure means, whereby said closure may be lowered into sealed assembly with said enclosure as the wellhead is lowered into said enclosure.
 4. A protective enclosure as recited in claim 1, an extension sleeve secured to the production conduit of said wellhead and moving into sealed assembly with the upper extremity of said enclosure as the wellhead assembly is lowered into said enclosure.
 5. A protective enclosure as set forth in claim 1, a fluid transfer connection being fixed to said closure and having an opening into said enclosure, means being received by said fluid transfer connection for remotely filling said enclosure with said corrosion and marine life inhibitors, a displacement conduit being fixed to said fluid transfer connection and terminating at the lower portion of said enclosure for remotely removing saiD corrosion and marine life inhibitors from said enclosure for servicing.
 6. A protective enclosure as recited in claim 1, guide means fixed to said enclosure and being connectable to a surface vessel, said guide means orienting said wellhead and said closure upon assembly thereof to said enclosure, said guide means also serving to guiding remotely controllable repair apparatus.
 7. Low profile wellhead installation and servicing apparatus comprising a conductor guide conduit extending a considerable depth into the surface stratum of the earth, a protective enclosure connected at the lower extremity thereof to said conductor guide conduit, the upper extremity of said enclosure being located adjacent the surface level of the surface stratum, a well casing extending through said conductor guide conduit and terminating in a casing hanger at the lower extremity of said enclosure, a wellhead assembly connected to said casing hanger and having its upper extremity disposed substantially at the surface level of the surface stratum, at least one production conduit extending from said wellhead assembly, a removable extension normally being disposed in sealed assembly with the upper extremity of said enclosure, said production conduit extending in sealed relation through said extension in generally horizontal manner substantially at the surface level of the surface stratum, a removable closure normally disposed in sealed assembly with the upper extremity of said extension.
 8. Low profile wellhead installation and servicing apparatus as recited in claim 7, guide means fixed to said enclosure and extending to a location remote from said wellhead installation, said wellhead assembly being oriented by said guide means upon installation thereof within said enclosure.
 9. Low profile wellhead installation and servicing apparatus as recited in claim 7, said extension defining a support rim, a service manipulator adapted to be guidingly supportable by said rim and being receivable within said enclosure, said servicing manipulator being oriented within said enclosure by the inner surface of said enclosure, said manipulator being capable of accomplishing various repair operations on said wellhead.
 10. A protective enclosure for subsea wellhead apparatus comprising a conductor guide conduit extending a considerable depth into the soft surface stratum of the ocean floor, a wellhead protective enclosure connected to the upper extremity of said conductor guide conduit, the upper extremity of said enclosure being located substantially at the level of the ocean floor, the inner surface of said enclosure defining annular guide surface means, said enclosure defining an annular manipulator support rim at the upper extremity thereof, external guide means secured to said enclosure and being attachable to surface vessel structure, repair manipulator means being guidable into assembly with said enclosure by said external guide means, said repair manipulator being supported by said manipulator support rim and being oriented within said enclosure by said annular guide surface means, said manipulator being capable of moving about within said enclosure and performing various repair operations.
 11. A protective enclosure system for a subsea wellhead assembly including a guide conductor extending a considerable distance into the surface stratum of the ocean floor, a protective enclosure fixed to the upper extremity of the guide conductor and having the upper extremity thereof disposed adjacent the surface level of the ocean floor, a cover member closing the upper extremity of the enclosure and preventing entry of foreign matter into said enclosure, fluid transfer apparatus secured to said cover and including a stabbing sleeve having a central opening, a fluid transfer conduit extending from said stabbing sleeve in fluid communication with said central opening and terminating within said enclosure, a drill stem having a stabbing pin disposed at the lower extremity thereof, said stabbinG pin being receivable within said stabbing sleeve, said stabbing pin having fluid passages therein to selectively allow the filling of said enclosure with a preservative substance and to displace said preservative material from said enclosure.
 12. A protective enclosure as set forth in claim 11, said stabbing pin having a pair of fluid transfer passages, one of said circuits being plugged to allow the filling of said enclosure with preservative and causing fluid to flow in one direction within said displacement conduit, the other of said fluid transfer passages being plugged to cause the flow of fluid through said displacement conduit in the opposite direction to cause displacement of preservative substance from said enclosure.
 13. A protective enclosure as set forth in claim 11, a closure being receivable within said stabbing sleeve to seal said enclosure, said closure having pressure balancing valve means therein to maintain a substantially balanced condition between said protective enclosure and the hydrostatic head of the sea water at the depth of the enclosure. 